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Feature
Mild X-ray radiation of food as an alternative to isotope-based irradiation
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Monday, 12 January, 2009, 08 : 00 AM [IST]
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V H Potty
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Food irradiation has been a subject of intense investigation for almost half a century and extension of shelf life of foods by gamma radiation is legally permitted in more than 40 countries covering a number of foods such as onion, potato, wheat, spices, flours, meat, poultry, fish, pulses, rice, semolina, fruits, vegetables and dry fruits. The Board of Radiation & Isotopes Technology (BRIT) under the Dept of Atomic Energy operates two irradiation plants for use by the industry at Nashik (for onions) and Navi Mumbai (for spices). In the private sector also such special facilities are being offered. Irradiation, also known as ionizing radiation technology, involves exposing the food to such radiations to kill micro-organisms like bacteria and viruses, insects and their larvae, inhibit sprouting, delay ripening, increase juice yield and improve re-hydration properties. World over 5,00, 000 tonnes of foods are irradiated annually and the business is projected to cross $ 2.3 billion in value by 2012.
X-Rays, a photon radiation of wide energy spectrum of short wave lengths, is an alternative to isotope based irradiation system and they are generated by colliding electrons with a dense material called a target such as Tantalum or Tungsten in a process known as Bremsstrahlung conversion. These rays have deep penetration capacity, comparable to Cobalt-60 with the added advantage of using an electronic source that stops radiation when switched off. They also allow dose uniformity which is desirable in any industrial process of food pasteurization. X-Rays have been found to be very efficient in killing E.coli 0157:H7 and Salmonella, two of the most virulent bacterial species causing food borne illnesses in many countries. While existing thermal and chemical interventions can eliminate pathogens, these methods are not satisfactory for delicate vegetables like spinach and other leafy materials, much sought after as a part of nutritious food menu world over. In packing sheds there are no steps during cleaning and washing, sorting and packing to destroy pathogenic microorganisms which might have originated in the field or the handling chain or as cross contaminants from other vegetables. Higher doses X-Rays (routinely used by medical profession) but much less than that used in irradiation, can be an effective tool in fighting pathogens that get access to human system through soft vegetables, without affecting the sensory quality of the treated materials.
One of the major advantages of X-Ray radiation is that investment for setting up the required facilities is affordable to the industry and each and every processor can set up the system within their premises for use as and when required. In contrast centralized facilities are called for establishing irradiation plants with all attending dangers and logistical problems. Unlike gamma radiation which invariably raises suspicion in the minds of the consumers because of its association with nuclear bombs, X-Ray machine is a familiar instrument in all hospitals and clinics with a favorable image. A major disadvantage is the relative inefficiency of the process which involves conversion of electrical energy to photo radiation requiring much more electricity than other systems.
Probably the Food Irradiation group in Bhaba Atomic Research Centre can look into this alternative option in the interests of the industry, if not already done. If found suitable from quality and sensory angles, they can try to design sound X-Ray machines at affordable cost, with provision for processing foods which are amenable to this treatment. Probably new processing protocols may have to be evolved with India-grown foods before commercializing the X-Ray technology. It is possible that the present image of India as an exporter of foods of uncertain microbial quality can be refurbished if X-Ray technology proves its potential, enabling most of the exporters in setting up these facilities themselves without depending on any external agency.
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